121 lines
2.3 KiB
C
121 lines
2.3 KiB
C
// Copyright (C) 2011 Valeriano Alfonso Rodriguez (Kableado)
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#include <math.h>
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#include "Util.h"
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/////////////////////////////
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// SolveQuadratic
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//
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// Solves a Quadratic equation using a, b and c coeficients.
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int SolveQuadratic(float a,float b,float c,float *Rmin,float *Rmax){
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float root;
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float divisor;
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float b2;
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b2=b*b;
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root=b2-4.0*a*c;
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if(root<0){
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// Complex
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return(0);
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}
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divisor=(2.0*a);
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if(fabs(divisor)==0.0f){
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// +inf -inf
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return(0);
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}
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root=sqrtf(root);
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Rmin[0]=(float)((-b-root)/divisor);
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Rmax[0]=(float)((-b+root)/divisor);
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return(1);
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}
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/////////////////////////////
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// Intersec_RayUnitCircle
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//
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// Intersection between a ray and a Unit Circle.
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int Intersec_RayUnitCircle(vec2 orig,vec2 vel,vec2 center,float *t){
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float a,b,c;
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float Rmin,Rmax;
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vec2 distv;
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float qlvel;
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float qdistv;
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// Check if the collision is even posible
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qlvel=vec2_dot(vel,vel);
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if(fabs(qlvel)<=0.0f)
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return(0);
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vec2_minus(distv,orig,center);
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qdistv=vec2_dot(distv,distv);
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// Solve as a unit circle
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a=qlvel;
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b=2.0f*vec2_dot(distv,vel);
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c=qdistv-1.0f;
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if(SolveQuadratic(a,b,c,&Rmin,&Rmax)){
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if(Rmin>=-0.0f && Rmin<Rmax && Rmin<=1.0f){
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*t=Rmin;
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return(1);
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}
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if(Rmax>=-1.0f && Rmin>Rmax && Rmax<=1.0f){
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*t=Rmax;
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return(1);
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}
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}
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return(0);
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}
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/////////////////////////////
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// Colision_CircleCircle
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//
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// Colision point of a circle against another circle.
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int Colision_CircleCircle(
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vec2 cir1,float rad1,vec2 vel,
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vec2 cir2,float rad2,
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float *t,vec2 n)
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{
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vec2 vel_a,orig_a,cen_a,temp;
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float rads,invrads;
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float maxx,minx;
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float maxy,miny;
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// Check if the collision is even posible
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rads=rad1+rad2;
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minx=cir1[0]-rads;
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maxx=cir1[0]+rads;
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if(vel[0]>0){
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maxx+=vel[0];
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}else{
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minx+=vel[0];
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}
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if(cir2[0]<minx || cir2[0]>maxx)
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return(0);
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miny=cir1[1]-rads;
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maxy=cir1[1]+rads;
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if(vel[1]>0){
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maxy+=vel[1];
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}else{
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miny+=vel[1];
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}
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if(cir2[1]<miny || cir2[1]>maxy)
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return(0);
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// Convert to a unit circle vs ray
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rads=rad1+rad2;
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invrads=1.0f/rads;
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vec2_scale(vel_a,vel,invrads);
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vec2_scale(orig_a,cir1,invrads);
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vec2_scale(cen_a,cir2,invrads);
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if(Intersec_RayUnitCircle(orig_a,vel_a,cen_a,t)){
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// Calculate n
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vec2_scale(temp,vel,*t);
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vec2_plus(temp,cir1,temp);
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vec2_minus(temp,cir2,temp);
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vec2_scale(n,temp,1.0f/rads);
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return(1);
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}
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return(0);
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}
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